With broadband access services being desired and accepted by more and more end users, the challenges of devising economically feasible optical access networks for providing broadband services to end users becomes increasingly important. Currently, typical Fiber-to-the-Home (FttH) systems deploy optical packet networks (e.g., Asynchronous Transfer Mode or Ethernet) that may substantially be characterized according to two main approaches, namely; Active Optical Networks (AONs) that utilize active fiber sites in the field, and Passive Optical Networks (PONs) that make use of a fully passive outside plant fiber.
AONs make use of relatively simple transceivers and switches using technology that originates from optical (e.g., Ethernet) data networks that, due to their volumes, are relatively inexpensive. Powered equipment in Access Concentrators in such networks is required to bridge restrictive transmission distances. The availability of power in the field also allows for different services, such as mobile telephony and wireless access, to be supported. However, such active equipment involves remote installation and the amount of components and the power they consume directly translates into maintenance requirements and high down-times that ultimately lead to additional operational expenses.
To avoid the presence of active components in the field, substantially all of the multiplexing and switching equipment of an AON may be located within a Central Office of the network. Such a network is known as a Point-to-Point network. An additional advantage of these networks is that they provide a dedicated physical medium to each subscriber, allowing for almost any change or upgrade. However, such a network consumes a considerable amount of power and space within the Central Office. In addition, for supporting existing analog services, such as broadcast television and radio, in such systems either complex optical multiplexers or expensive encoders must be installed within the Central Office and decoders must be installed in user (customer) equipment.
To overcome the problems associated with AONs, PONs were developed. By using passive tree-and-branch fiber infrastructures the amount of equipment at a Central Office may be reduced. In addition, broadcast services may be simply implemented, including analog broadcast service which may be supported by means of coarse wavelength division multiplexing. However, in current PONs complex and expensive asynchronous transmission technology and equipment is required in the upstream direction of communication. In addition, the use of passive power splitters/combiners in such networks limits the aggregate bandwidth that may be made available to users.